package deap;

import java.util.Arrays;

public class PriorityQueue {
    public int[] elem = new int[11];
    public int usedSize;

    public PriorityQueue() {

    }
    public void print(){
        for (int i = 0;i<usedSize;i++){
            System.out.print(elem[i]+" ");
        }
    }

    /**
     * 建堆的时间复杂度：
     *
     * @param array
     */
    public void createHeap(int[] array) {
        if (array.length > elem.length) {
            // 扩容逻辑
            elem = Arrays.copyOf(elem, array.length);
        }
        for (int i = 0; i < array.length; i++) {
            this.elem[i] = array[i];
            this.usedSize++;
        }
        for (int i = (usedSize-2)/2; i >=0; i--) {
            shiftDown(i,usedSize);
        }

    }

    /**
     *
     * @param root 是每棵子树的根节点的下标
     * @param len  是每棵子树调整结束的结束条件
     * 向下调整的时间复杂度：O(logn)
     */
    private void shiftDown(int root,int len) {
        int child = root*2+1;
        while (child<len){
            if(child+1<len && elem[child+1]>elem[child]){
                child++;
            }
            if(elem[child]<=elem[root]){
                break;
            }
            int tmp = elem[child];
            elem[child] = elem[root];
            elem[root] = tmp;
            root = child;
            child = root*2+1;
        }
    }


    /**
     * 入队：仍然要保持是大根堆
     * @param val
     */
   //在usedSize位置插入数据 再向上调整
    public void push(int val) {
        elem[usedSize++] =50;
        shiftUp(usedSize-1);

    }

    private void shiftUp(int child) {
        int parent = (child-1)/2;
        while (parent>=0){
            if(elem[parent]>=elem[child]){
                break;
            }
            int tmp = elem[child];
            elem[child] = elem[parent];
            elem[parent] = tmp;
            child = parent;
            parent = (child-1)/2;
        }
    }

    public boolean isFull() {
        return usedSize==elem.length;
    }

    /**
     * 出队【删除】：每次删除的都是优先级高的元素
     * 仍然要保持是大根堆
     */

    //先把对顶元素和最后一个元素交换，use--，堆顶再向下调整一次
    public void pollHeap() {
        elem[0] = elem[--usedSize];
        shiftDown(0,usedSize);
    }

    public boolean isEmpty() {
        return usedSize==0;
    }

    /**
     * 获取堆顶元素
     * @return
     */
    public int peekHeap() {
        return elem[elem.length-1];
    }
}
